The present invention generally relates to an electric-powered motor. The present invention pertains to a control device for an electric-powered motor and a designing method thereof.
SR motors (i.e., switched reluctance motor) have been known as traction motors for electric vehicles. According to general controls for the SR motors, a target torque Req_trq is calculated based on an operation amount of a throttle pedal (i.e., throttle opening degree) and the target torque Req_trq is converted into a command value to the SR motor using a predetermined map to be given to the SR motor. Thus, the SR motor is controlled for generating a torque in accordance with the target torque Req_trq.
A control system for the aforementioned SR motor is configured to have an open loop. When a vehicle applied with the foregoing SR motor includes the resonance characteristic due to the torsion of a shaft and tires and the influence of a suspension spring, the motor rotation speed is resonant relative to, for example, the sudden change of the target torque to cause the vibration in longitudinal direction of the vehicle. This vibration gives an annoyance to occupants.
In order to restrain the above-explained vibration, an SR motor controlled by applying H∞ control theory has been proposed.
FIG. 21 shows a detail of the control of an SR motor including a controller K (i.e., H∞ controller) designed using the H∞ control theory. That is, the target torque Req_trq is calculated based on the throttle opening degree in this control system, then the target torque Req_trq is converted into the command value to the SR motor by the predetermined map to be given to the SR motor. In this case, the target torque Req_trq is corrected by a feedback correction amount u calculated in the controller K based on the motor rotation speed Nm.
FIG. 22 is a time chart showing a response characteristic (i.e., motor rotation speed characteristic) when generating a stepped input by suddenly changing the target torque Req_trq by stepping on or releasing the throttle pedal during the control of the SR motor. That is, each motor rotation speed characteristic according to the open-loop control and the H∞ control relative to the sudden change of the target torque Req_trq is shown. As shown in FIG. 22, the vibration (i.e., resonance) of the motor rotation speed relative to the stepped input is restrained by performing the H∞ control compared to the case performing the open-loop control.
With the H∞ control problem mainly featuring the robust stability problem (i.e., securing the robust stability), when the performance requirement relative to the robust stability is extremely high, the performance of the tracking performance (i.e., vibration reduction and torque tracking performance) which has trade-off relationship with the robust stability is deteriorated. Thus, the high performance SR motor control in which high robust stability and the tracking performance are compatible is desired.
A need thus exists for a control device for an electric motor and a designing method thereof in which the high robust stability and the tracking performance are compatible with each other.
In light of the foregoing, the present invention provides a control device for an electric motor which includes an electric motor, a detection means for detecting a motor rotation speed of the electric motor, a calculation means for calculating a target torque of the electric motor, a feedback compensator for obtaining a feedback correction amount based on the detected motor rotation speed, a feedforward compensator for obtaining a feedforward correction amount based on the calculated target torque, and a control means for commanding a torque control to the electric motor based on the feedback correction amount and the feedforward correction amount.